The most important mineral which is used as a raw material for the production of strontium compounds is celestite. It consists predominantly of strontium sulfate and is usually contaminated with barium compounds. Because strontium compounds are used in certain fields of technology, for example in the manufacture of color television picture tubes, in the production of ceramic permanent magnets and as an additive for toothpastes, it is frequently desirable to separate the naturally occurring barium content from strontium salts.
For a long time, there has been an intensive search for methods for separating barium from strontium compounds.
Precipitation by means of chromate was for a long time the only industrially usable method for separating barium from strontium salts. Chromate is toxic, however, and must therefore itself be removed from the resulting strontium salt by extensive purification operations.
Another industrially applicable method is disclosed in published German patent application DE-OS No. 1,816,891. In this published application, the separation of barium is effected by means of the compound SrSO.sub.4.2H.sub.2 O which, if desired, is also produced in situ by addition of sulfuric acid. This type of separation is, however, not easy to control, since strontium sulfate dihydrate is formed only under very definite, narrowly limited reaction conditions.
The hitherto known processes for separating barium from water-soluble strontium compounds thus have the disadvantage of involving the introduction of toxic materials or of being not easily carried out industrially.